M51 (LHaRGB) 26 April 2020

[geoflewis]

Here is my version of M51 a target that I've only imaged twice before, once when I was just starting out imaging in 2013 with a DSLR attached to my 10" Meade LX200 and then again some 5 years ago in April 2015 also with a DSLR but attached to my then new 4" TSAPO100Q, a much wider field view, so I thought that was about time that I revisited it with my C14 and mono QSI585wsg-5 camera.

The image comprises L=36x10m, Ha=11x15m, RGB(each)=24x5m for a total integration of just under 15 hours. I used ImagesPlus mix LRGB tool to create a colour image blending 20%Ha and 80%R for the red channel, so as not to overly saturate the active Ha regions in the galaxy (it may still be too much). The L was separately processed and layered over the HaRGB using ImagesPlus with final tweaks in PS(CS2).

Revision with reduced magenta and pass through Topaz denoise which trial I've just downloaded....

Thanks for looking, as always comments and feedback are very welcome.

 

Edited April 27, 2020 by geoflewis
added revised image

[JamesF]

Very nice,Geof.  Nice clear image of that edge-on galaxy at the top right, too.

I need to get around to reprocessing mine now the weather looks like there's going to be little opportunity to get out for a few days.

James

[lux eterna]

Nice catch with the diffuse surrounding areas clearly visible. On my screen I see a little magenta bias so I gave it a try in PS to get a bit more colour separation (colour contrast). Used curves, selective colour, HLVG and hue/saturation (hope you dont mind).

Ragnar

[geoflewis]

2 minutes ago, lux eterna said:

Nice catch with the diffuse surrounding areas clearly visible. On my screen I see a little magenta bias so I gave it a try in PS to get a bit more colour separation (colour contrast). Used curves, selective colour, HLVG and hue/saturation (hope you dont mind).

Thanks Ragnar, no I don't mind at all. I also saw the magenta hues and have been playing with it in PS too, but think I got processing blindness from looking at it too long, so out it up for feedback, so your's is much appreciated. Adding the Ha data really threw the colours off, so I'll take another look at it later.

[Gina]

Excellent image Geof - well done.  Beats my attempts of the past.  This is my favourite galaxy and feel inclined to have another go at it.

[geoflewis]

8 minutes ago, Gina said:

Excellent image Geof - well done.  Beats my attempts of the past.  This is my favourite galaxy and feel inclined to have another go at it.

Thanks Gina, it really is a beautiful galaxy and I couldn't believe how long it had been since I imaged it. I think I've been too focused on capturing as many different Messier targets for my collection as I can, that I forget to go back and improve on the ones I did several years ago. This year I've redone M81, M82 and now M51, so next year I think I'll have another go at M101.

[Laurin Dave]

Very nice Geof..  my favourite too and it snice to revisit them !  I'm not familiar with the Images Plus processing package but I wonder if its blending Ha with Red that gives it the magenta tinge?  As you have Photoshop it might be worth making an RGB image and then adding Ha to the Red in blend mode lighten before layering on the luminance and seeing what that gives (maybe you can also do this in Images Plus) 

Dave

[geoflewis]

Just now, Laurin Dave said:

Very nice Geof..  my favourite too and it snice to revisit them !  I'm not familiar with the Images Plus processing package but I wonder if its blending Ha with Red that gives it the magenta tinge?  As you have Photoshop it might be worth making an RGB image and then adding Ha to the Red in blend mode lighten before layering on the luminance and seeing what that gives (maybe you can also do this in Images Plus) 

Dave

Thanks Dave,

Yes, ImagesPlus (IP) does allow blending Ha with R first before building the RGB image, in fact in many respects IP mirrors what can be done in PS. There seem to be so many methods for combining Ha with RGB data, but I struggle with them all.... 🥴. I guess practice will get me closer to perfect, not sure how close though.....

[Laurin Dave]

5 minutes ago, geoflewis said:

Thanks Dave,

Yes, ImagesPlus (IP) does allow blending Ha with R first before building the RGB image, in fact in many respects IP mirrors what can be done in PS. There seem to be so many methods for combining Ha with RGB data, but I struggle with them all.... 🥴. I guess practice will get me closer to perfect, not sure how close though.....

Does it allow (as PS does in blend mode lighten) to just include the actual Ha regions?..  What you'd do in PS is take your lightly stretched RGB image, duplicate it, split the channels throw away G and B and then paste your lightly stretched Ha over Red.. change blend mode to lighten .. add a levels layer acting only on the Ha layer and adjust that to bring out the Ha regions..  then Select all copy merged and paste back into the RGB image as the new Red..  then layer on your luminance for the final result..  

[geoflewis]

1 minute ago, Laurin Dave said:

Does it allow (as PS does in blend mode lighten) to just include the actual Ha regions?..  What you'd do in PS is take your lightly stretched RGB image, duplicate it, split the channels throw away G and B and then paste your lightly stretched Ha over Red.. change blend mode to lighten .. add a levels layer acting only on the Ha layer and adjust that to bring out the Ha regions..  then Select all copy merged and paste back into the RGB image as the new Red..  then layer on your luminance for the final result..  

Yes, IP has all the same blend modes as PS. I have tried lighten blend previously, but will give it another try. Thanks for the suggested workflow, I’ll take another look at processing it. This is where this forum is so helpful. Many thanks

[carastro]

Excellent work Geoff. 
 

carole

[geoflewis]

45 minutes ago, carastro said:

Excellent work Geoff. 
 

carole

Thanks Carole, I'm very pleased to get a better version of this beautiful galaxy.

[LongJohn54]

Excellent image.  I'll be using that as my reference image when I process my M51.   👍

[bdlbug]

Wow - love the image and seriously impressive that you have captured  this with round stars  across the FOV. Guiding with 4m focal length telescope and imaging at <0.3" per pixel, Hats off to you and your setup
(I sold my C11 as I never thought I could ever use it effectively for DSO imaging)

Bryan

[geoflewis]

5 minutes ago, bdlbug said:

Wow - love the image and seriously impressive that you have captured  this with round stars  across the FOV. Guiding with 4m focal length telescope and imaging at <0.3" per pixel, Hats off to you and your setup
(I sold my C11 as I never thought I could ever use it effectively for DSO imaging)

Bryan

Thanks Bryan,

So for clarification I have an Optec telecompressor lens designed specifically for the classic (non Edge) C14 which does a great job, though still not totally flat field. It aso reduces the FL to around 2.6m. Even then the system would be significantly oversampled with the QSI583, so I also bin 2x2 for all subs, getting me to about 0.86"/px. Guiding with the Lodestar X2 was in the range 0.4"-0.5", so well inside the imaging scale, which is good. The major player in imaging at this scale is the Astro-Physics 1200 mount, which is massive with minimal PE or backlash, so I can let it get on with the job with few worries.

[geoflewis]

For anyone interested I took Ragnar's (@lux eterna) advice and adjusted the colour balance to get rid of the magenta hue and also ran it through Topaz Denoise. I've uploaded the revised image below the original at the start of this thread, so that it is easier to compare them. I will likely do a complete rework to see if I can improve the original Ha blend using a lighten blend as suggested by @Laurin Dave, but not today.

Thanks everyone for the very helpful feedback; more is also welcome...

[bob-c]

A great image this is Geof ,and great processing very well don.

Bob.

[geoflewis]

2 minutes ago, bob-c said:

A great image this is Geof ,and great processing very well don.

Bob.

Thanks Bob, the quality of the image has a lot to do with the advice and guidance I've received from folks on this forum, not only for this image, but over several years.

[tingting44]

thats stunning! the difference is night and day! i love it

[geoflewis]

Thanks Martin, that's the kind of feedback I love, I'm so glad that you like the revisions, it makes it all worthwhile.

[ollypenrice]

6 hours ago, geoflewis said:

Thanks Dave,

Yes, ImagesPlus (IP) does allow blending Ha with R first before building the RGB image, in fact in many respects IP mirrors what can be done in PS. There seem to be so many methods for combining Ha with RGB data, but I struggle with them all.... 🥴. I guess practice will get me closer to perfect, not sure how close though.....

The problem with a straight blend of Ha-red is that the Ha stars are much smaller, so the final stellar colour balance will be affected. The background will be darker, too, so you'll need to rebalance that. Also not all the red signal comes from Ha so that which doesn't will be diminished by a blend. Blend mode lighten is 'add only,' hence its charm.

Did you capture in Bin 1?

Anyway it's a nice result.

Olly

[geoflewis]

13 minutes ago, ollypenrice said:

The problem with a straight blend of Ha-red is that the Ha stars are much smaller, so the final stellar colour balance will be affected. The background will be darker, too, so you'll need to rebalance that. Also not all the red signal comes from Ha so that which doesn't will be diminished by a blend. Blend mode lighten is 'add only,' hence its charm.

Did you capture in Bin 1?

Anyway it's a nice result.

Olly

Hi Olly,

Thanks for the feedback and advice, it sounds like I really must get to grips with using lighten blend mode for HaRGB combine, something for me to do over the forecast run of cloudy nights and rainy days coming up. No not Bin 1, I shoot all my data with the C14 at Bin 2 due to the significant oversampling that I'd get at Bin 1 with the QSI583 camera.

[geoflewis]

Hi Olly @ollypenrice and Dave @Laurin Dave

Today I've been experimenting with the lighten blend mode to combine Ha with R, but need some further clarification please. Should both the Ha and R be set to lighten mode, or just one or the other and if just one of them, which channel should be on top of the other in the stack. I seemed to get the best results with both set to lighten, but I think it is pretty much the same if either one is set to lighten provided it is the top one in the stack. Am I on the right track please? I had to stretch the images to play with the various blend options as I couldn't see what was going on with the unprocessed raw stacks, as all was just black....!!

Many thanks in advance.

[Laurin Dave]

3 minutes ago, geoflewis said:

Hi Olly @ollypenrice and Dave @Laurin Dave

Today I've been experimenting with the lighten blend mode to combine Ha with R, but need some further clarification please. Should both the Ha and R be set to lighten mode, or just one or the other and if just one of them, which channel should be on top of the other in the stack. I seemed to get the best results with both set to lighten, but I think it is pretty much the same if either one is set to lighten provided it is the top one in the stack. Am I on the right track please? I had to stretch the images to play with the various blend options as I couldn't see what was going on with the unprocessed raw stacks, as all was just black....!!

Many thanks in advance.

I have the Red at the bottom in Normal mode and put the Ha on top of that in Lighten mode..  the Red comes from copying and channel splitting  a lightly stretched and saturation enhanced RGB combination ( I find the overall colour is better after Lum layering if the RGB  isn't stretched too much) and the Ha is also stretched so that the HII regions are about the same as they are on the Red channel..  I then apply a Levels adjustment layer to the Ha only, pull the back point in and adjust the mid point slider to taste..  Select All, Copy Merged and paste into the RGB image...  ( I generally iterate a bit with the Ha  levels layer until it looks most pleasing  (well to me!))  .. I then do the Luminance layering..   Olly may have a smarter way of doing this... ( I knew I should have taken notes!) 

HTH...   

Dave

[geoflewis]

4 minutes ago, Laurin Dave said:

I have the Red at the bottom in Normal mode and put the Ha on top of that in Lighten mode..  the Red comes from copying and channel splitting  a lightly stretched and saturation enhanced RGB combination ( I find the overall colour is better after Lum layering if the RGB  isn't stretched too much) and the Ha is also stretched so that the HII regions are about the same as they are on the Red channel..  I then apply a Levels adjustment layer to the Ha only, pull the back point in and adjust the mid point slider to taste..  Select All, Copy Merged and paste into the RGB image...  ( I generally iterate a bit with the Ha  levels layer until it looks most pleasing  (well to me!))  .. I then do the Luminance layering..   Olly may have a smarter way of doing this... ( I knew I should have taken notes!) 

HTH...   

Dave

Thanks Dave,

I think I follow this, at least the bit about which is channel set to lighten and where it is placed in the HaR stack, however, I'm a bit confused by the part that I've highlighted in bold italics above. Are you building an RGB image from mono data first, then stretching that before splitting out the red to combine with the Ha, or is your data from a DSLR or OSC camera?